In recent years, the number of patients suffering from respiratory system diseases such as asthma, pulmonary emphysema, chronic bronchitis and the like has tended to increase. One of the most effective therapeutic methods for these diseases is oxygen inhalation therapy. In such oxygen inhalation therapy, oxygen gas or oxygen-enriched gas is inhaled by patients. An oxygen concentration device, liquid oxygen or oxygen gas cylinder, and the like are known as an oxygen supply source used for the oxygen inhalation therapy. However, an oxygen concentration device is mainly used for home oxygen therapy because it is convenient to use and easy for maintenance and management.
An oxygen concentration device is a device to supply oxygen to a user by separating and concentrating oxygen that makes up 21% of the air. As such device, there are a membrane-type oxygen concentration device that uses a membrane which selectively permeate oxygen and a pressure swing adsorption-type oxygen concentration device that uses an adsorbent which can preferentially adsorbs nitrogen or oxygen. A pressure swing adsorption-type oxygen concentration device is mainly used because it can obtain highly concentrated oxygen.
The pressure swing adsorption-type oxygen concentration device continuously produces a highly concentrated oxygen gas by repeating alternately a compression-adsorption step and a decompression-desorption step. In the former step, un-adsorbed oxygen is obtained by supplying air compressed by a compressor to an adsorption cylinder filled with an adsorbent which selectively adsorbs nitrogen relative to oxygen, such as 5A, 13X, or Li—X type molecular sieve zeolites, and adsorbing nitrogen under pressurized conditions. In the latter step, the adsorbent is regenerated by purging nitrogen adsorbed on the adsorbent under a reduced pressure of atmospheric pressure or less in the adsorption cylinder.